Electric heater.



R.` H. READ.

ELEGIRIG HEATER. APPLIGATION FILED JAN. 3, 1914.

1,127,874.. l. PatenteaFeb.2,1915.

34a/vento@ UNITED sTATEs PATENT OFFTCE. ROBERT H. READ, or WASHINGTONDISTR'ICT oE coiwiunra.v AssIGNOR To GENERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK.l v

'ELECTRLC HEATER.

To all/107mm t may concern.'

Be it known that I ROBERT H. READ, al

' the electrical heating element relatively to o way. Moreover the heating element or core' the heat transmitting support on'which it is mounted.

In a priorl application filed by me, Serial Number 485,329 I have described a heater of this character.

My present improvements relate to a parf ticular form of connecting the heating ele-v ments in circuit with supply wires by which perfect freedom of expansion Aof the heater wireA is afforded. The particular heating element employed in the present structure as well as in that already referredto consists of, a high resistance heater-element 'formed of a metal or alloy of very high 'specific resistance surrounded by a closelyv packed powdered mineral insulation and inclosed in a metallic armor or sheath,the whole being metallically united on theoutside of the sheath with a heat transmittin communicate bythe best possib e thermal relation the heat of the element to a body through which lthe heat is tobe diffused either by radiation or conduction. Now the. metallic armor by reason of its'rigid bond with the supporting plate is afforded small opportunity of expansion, the latter being absorbed incrementially bythe support; the resistance wire howeverV being locked only by the hard packed mineral insulation is relatively comparatively free to expand and develops a strain at the ends where it is connected to an external circuit, forcing the joint at that pointto be distorted or Ato give wire itself if allowed to protrude from the powder or insulation becomes highly heatedl where it is bathed in the air and by repeated Specication of Letters Patent. .application mea January s, 19'144. serial No. 810,175.

plate to` rateiited Feb. e, 1915.

flexure under successive heatings and coolyings is liable to break off.

My present improvements are directed vto a cure for both of these-objectionablefeatures, in that I provide for the expansion of the core-wire by a ieXible connectlon or lead connecting the same with the fixed-circuit terminals and in that I also terminate the core` within the end of the'wire itself'where it is surrounded by insulating powder, connecting it at its terminus lwith a lead-Wire of 4greater conductivity, as for example, one of greater cross-section or one of less specific "resistance, which will not heat under the the armor and core vwire without nected by a joint with a better conducting terminal, which joint is afforded heat diffus prevent excessive heating of vthe core-wire. f

ing means to Other features of novelty -ofmy invention will be more particularlyl hereinafter de'- scribed and will beA definitely indicated in theclaims appended to this specification:

. vIn the accompanying drawing which illus- ,trates my invention: Figure 1 represents a portion of a heater very much magnified in dimensions embodying my improvements. Fig.v 2 is a view of the devlce shown-in Fig. 1 shown on a plane lat right angles to that of the latter figure. Fig. 3 is a similar view to Fig. 2 showin a modification in which a ribbon termina isempIOyed, and Fig. 4

is a bottom plan showing on a smalll scale'` the heating element and its ing to my lnvention.

Referring now more particularly to .the drawings, 1 represents a radiator vor heat diifuser consisting of a metallic plate which radiator accordwelding or other integral means of forming a metallic union with the plate 1s an armored wire consisting of a core-wire 2, surrounded by mineral insulation 3. both being inclosed in a tubular metallic shell 4.

I have heretofore fully disclosed a wire of this kind in other applications, as for eX ample, thatabove. referred to: the core wire 2 is made of metal or alloy of high specific resistance suchas nickel iron, nickel chromium or nickel manganese. The refractory insulating powder should be highly compacted between thecore-wire/ and its armor 4, and is preferably ofv a composition suiiiciently heat refractory not to approach its fusing point at the temperatures to which the core-wire is run in service, such as material made of suchmineral oxids or silicates as finely divided flint, magnesia, kaolin. soapstone, or in general any material which is at once a good insulator' and fairly good heat conductor and has a high fusing point.

have found excellent results with finely di= vided flint of a high degree of ineness which in the process of manufacture of the armored'conductor is highly compacted within the armor and affords anpeasyv path for diffusing heat. givenfpflz' bythe .core and its transmission to the supporting plate or anyV medium which surrounds it.- This wire is preferably wound in a spiral as indicated in Fig. 4both ends being carried spirally outward and terminating on the exterior of the supporting plate in binding posts or other terminals 5 5 by which communication with a supply-circuit may be made.

At the vpoint where the lead wires are joined to the supply circuit I provide a yielding terminal 6-611 this may be a simple helix by which flexibility relative to the xed terminals is'aii'orded, or it may be a tape-like lead 7, see Fig. 3, sufficiently flexible to yield and provide for such expansion as may be created by the heat. I preferably makethis yielding terminal of m'aterialof better conductivity than the vcore-wire and -joint it with the latter so that thev joint is relatively cool `compared tothe temperature of the core-wire itself; this may be effected in a variety of ways as for example by making the terminals of a good conducting metal as copper and inclosing the joint with the core-wire within a heat diffusing medium. @ne convenient way of effecting this result is to form a tubular terminal 9 united by solder or otherwise with the armor and filh ing it with a heatrefractory powder, as

flint, whereby the joint is in good thermal rel lation to the tubular tip ,'9 maintained relatively cool" by the 4radiating surface of the tube which may be extended if desired by one or more metallic radiators l0, secured to the tip.' in fact the projecting terminals 6-6 if of copper will by reason of its high conductivity carry away heat from the joint sufficiently fast to keep the latter at a relatively low temperature. Where-the terminal prctrudes is a lava or soap-stone bushing 1l around which the terminus of the tip is crimped, as indicated at 12, to form a secure mounting for it. Thus it will be seen 1. An electric heater comprising an arl mored wire consisting of a core of high specific resistance. a refractory/insulating powder surrounding the same and inclosed within a metallic tube, and terminals con necting with a supply circuit free to accommodate relative movement of the armor and core-wire to relieve strain on the core-wire.

2. An electric' heater comprising a heat distributing plate,..an armored heater wire metallically bonded thereto and inclosed Within a metallic tube, a spacing of heat refractory mineralinsulation between the wire and yits armor, and Hexible terminals connecting the wire with fixed supply-circuit terminals. vf

3. An electric heater comprising an armored wire of' highspecificresistance, the armor being metalliceand confining the wire centrally within a body of heat refractory mineral insulation, and a terminal of relatively greater current carrving capacity than the wire connected thereto by a metallic joint, said terminal being adapted to yield relatively-to the fixed circuit-terminal.

4, An electric heater comprising an armored wire of high specific resistance, the armor being metallic and confining the wire centrally within a body of heat refractory mineral insulation, and a terminal of relatively greater current carrying capacity than 'the wire connected thereto by a metallic.

a tubular metallic armor, a terminal theresistance, a packin of heat refractory minfor extending through altip of insulating eral insulatlon am? material, and a heat radiator for keeping the being flexed spirally from the center outterminal cool. 4 ward at both ends. v 5 6. An electric .heater comprising 'a heat y ROBERT H. READ. distributing plate and an armored wire me. Witnesses:

tallically bonded thereto, said wire being E. A. CHAUNCEY, composed of a core wire of high specific r- A JULIEN E. MATTERN.

a-tubular armor, 4the xvire 1o 

